Cutting semi-plastic bodies



July 30, 1968 K. G. OLSSON ETAL. 3,395,204

CUTTING SEMI-PLASTIC BODIES Filed Nov. 9, 1964 United States Patent 3,395,204 CU'ITIN G SEMI-PLASTIC BODIES Karl Gustav Olsson, Solna, and Rolf Erik Giiransson, Handen, Sweden, assignors to Internationella Siporex Aktiebolaget, Stockholm, Sweden, a Swedish joint-stock company Filed Nov. 9, 1964, Ser. No. 409,753 Claims priority, application Sweden, Nov. 12, 1963, 12,443/ 63 7 Claims. (Cl. 264-157) ABSTRACT OF THE DISCLOSURE In wire-cutting unhardened, semiplastic cellular light weight concrete bodies into blocks or slabs smooth cut surfaces are obtained by passing through each cut formed by a first cutting wire at least one second wire following the path and direction of said first wire in relatively close succession thereto, each second wire having a diameter sufliciently large to let it contact at least the surface irregularities left behind by the preceding wire and possibly widen the cut. Longitudinal movements may be imparted to the wires, preferably in mutually opposite directions.

In manufacturing cellular light weight concrete products particularly for building purposes it is common practice to first mold relatively large bodies of a light weight concrete mass, which in any suitable way is made cellular or porous, and to then out these larger bodies into smaller pieces, such as blocks or slabs, of desired size and shape while the cellular mass of the body is still in a semi-plastic, unhardened condition. Such cutting is commonly carried out by means of wires or slender cords, e.g. of steel, which are caused to pass through the semiplastic concrete mass in a direction forming an angle to their own longitudinal direction to thereby produce the desired cuts in the body.

This process, known as the wire cutting method, offers great advantages over the other known method sometimes used in dividing up cellular light weight concrete bodies and which comprises sawing the molded bodies first when the latter have been already hardened, but nevertheless the wire cutting method is not completely satisfactory in the way it has hitherto been applied. Thus, the wire cutting method in its earlier fashion renders cut surfaces of a rather coarse structure, which fact makes the wire cut light weight concrete products less adaptable to certain applications within the modern building industry and, above all, makes the light weight concrete pieces separated by the cuts more liable to again bind together or cake during the steam hardening process, which ordinarily follows the cutting operation, so that the pieces must be forced apart in a rather rough manner easily resulting in a considerable rejection percentage. In addition the cut up products will present a very dust-laden surface after having been steam hardened so that they are rather disagreeable to handle.

Consequently, there is a demand for an improved method of cutting semi-plastic light weight concrete bodies by means of wires or cords making it possible to obtain cut surfaces which are at least approximately smooth and, consequently, not giving off so much dust after steam hardening and which, above all, show no tendency to again bind together or unite once the cutting operation has been finished.

The present invention has for its object to meet this demand and relates to a modified wire cutting method which is chiefly characterized in that at least two wire sections or card sections are caused to pass through the body the one behind the other in relatively close order to oo- "ice operate in producing one and the same cut. The foremost wire section, as calculated in the cutting direction, then effects the actual cutting while the subsequent wire section or wire sections will have a smoothing and probably also compressing effect on the cut surfaces left behind by the first Wire section.

Preferably two or more wire sections or card sections of different thicknesses are caused to pass through each cut, each thinner Wire section being followed by a thicker one. The thicker wire section or cord section should then suitably have a thickness which is not more than twice the thickness of the preceding wire section or cord section. However, there may also be used two or more wire sections or cord sections of the same thickness to produce one and the same cut, because the first or fore wire section, i.e. the actual cutting wire section, will, as a consequence of the surface imperfections referred to hereinbefore, always leave behind a cut having a free or open width which is smaller than the diameter or thickness of said first wire section or cord section.

It has been found particularly advantageous to carry out the method according to the invention by means of wire sections or cord sections which are caused to move longitudinally during their passage through the semiplastic "body in the cutting direction. In such a case the wire sections or cord sections may, if desired, be provided with sawtooth-like projections, but this is not in any way necessary since also completely smooth wires or cords will render a more favorable cutting result when the combined movement referred to is used.

The movement of the wire sections or cord sections in their longitudinal direction may be either continuous or reciprocative. In both cases the speed of longitudinal movement should be moderate in relation to the speed at which the Wire section or cord section is passing through the body in the cutting direction. It has been found most desirable to co-ordinate the movements of the Wire sections following each other in the same cut in such a manner that, if the foremost wire section, as calculated in the cutting direction, passes a certain surface portion in the cut while moving longitudinally in the one direction, the very next Wire section will move longitudinally in the opposite direction while passing the same surface portion. In practice, however, such an ideal co-ordination is sometimes difficult to achieve, particularly if reciprocat-ory movements are imparted to the wire section, and practical tests have proved that acceptable results can be obtained also without it.

The use of two wire sections in the same out according to the invention has proved to allow for an increase of the cutting speed as compared with the method hitherto practiced, and the use of e.g. three wire sections instead of two will make a still further increase of the cutting speed possible without in any way impairing the improved quality of the cut surfaces.

Besides improving the structure of the cut surfaces the use of two or more stretched wire sections or cord sectionsfollowing each other in each cut will, of course, give the advantage that there will always be a remaining Wire section capable of finishing the cut throughout the body, should the first wire sectionwhich is subjected to the heaviest strain'break as, unfortunately, happens rather frequently.

Although it is most common practice to use solid metal wires of substantially circular cross-section for carrying out the cutting operation there is nothing preventing the use of composite wires or strings or cords comprising several twisted strands. In the following text and in the appended claims the word wire has been used to define any such slender cutting member resembling a wire or cord in general appearance although it may have a flattened or otherwise irregular cross-section.

For further elucidation of the invention reference is made to the accompanying drawing, in which FIG. 1 is a perspective view illustrating in a very diagrammatic manner the application of the invention for cutting a semi-plastic, unhardened light weight concrete body,

FIG. 2 is a fragmentary surface view of a light weight concrete body through which two cutting wires section are passing to produce a dividing cut therein,

FIG. 3 is a diagrammatic sectional elevation of a first form of cutting apparatus taken along a plane in which two wires section forming part of an endless wire loop are passing through a semi-plastic light weight concrete body to produce in cooperation a cut therein,

FIG. 4 is a diagrammatic sectional elevational of a second form of cutting apparatus taken along a plane in which two wires section are passing through a semi-plastic light weight concrete body to produce in cooperation a cut therein,

I FIG. 5 is a diagrammatic sectional elevation similar to that of FIG. 4 but showing a modified form of cutting apparatus and FIG. 6 is a diagrammatic sectional elevation of a fourth form of cutting apparatus using two entirely separate wires to produce a cut in a semi-plastic body.

In all the figures a semi-plastic body B, for instance of cellular, 'unhardened light weight concrete, is being divided up or cut by being moved relative to two vertically stretched wire sections 1 and 2 respectively which are substantially parallel and located the one behind the other in line with the direction of cutting. Obviously, the cutting may equivalently be accomplished in such a manner that the wire sections 1 and 2, which are supposed to be stretched in a frame, a yoke or a similiar holding device, are moved relative to the body B in the intended direction of cutting. The two wire sections 1 and 2 will then together produce a cut 3, the first or fore wire section 1 as viewed in the cutting direction performing the actual cutting operation while the following wire section 2 serving to smoothen the cut surfaces left behind by the foremost wire section, the said surfaces presenting as shown at 4 in FIG. 2 a very rough and irregular structure of a scaly or thorny appearance.

The thickness of the wire section 2 can either be the same as that of the wire section 1 or, more preferably, somewhat larger. The difference in thickness should, however, not be exaggerated since this may hazard the result. Thus, the following wire section 2 should be no more than twice as thick as the foregoing wire section 1 and, at least when cutting is accomplished with round wires section having no kinds of saw teeth, the diameter of each subsequent wire section should preferably not be chosen larger than 50% above the diameter of the next foregoing wire section in the same cut.

The Wires section 1 and 2 may very well be two portions of a continuous wire length or of an endless wire loop, in which case the two wire portions are, of course, of the same thicknesses. In such a case this wire loop may, as indicated in FIG. 3, run over two pulleys 5 and 6 respectively, at least one of said pulleys being driven so that the portions 1 and 2 of the wire loop are caused to move in their longitudinal direction during their passage through the light weight concrete body B. In this way the foremost wire portion 1 will, of course, always move longitudinally in opposite direction to the following wire portion 2 and this has proved advantageous to obtain a good smoothness of the cut surfaces as well as a reduced risk of the cut surfaces again caking together.

Particularly if it is desirable to use differently sized wires section 1 and 2 it will be necessary to use other arrangements for imparting to the wires section their advantageous longitudinal movement. FIG. 4 illustrates by wayof example, how the two wires section may be stretched between two lever-like attachments 7 mounted on parallel rocking shafts 8, to which a reciprocating rotary or swinging motion is imparted in any suitable manner, so that the foremost wire section 1 will move upwards when the 'rear wire section 2 moves downwards, and vice versa. FIG. 5 shows another arrangement for the same purpose, in which the two wires section 1 and 2 respectively are entirely independently movable by being stretched between each onepair of rocker arms 9 and 10 respectively, which are driven in a suitable manner. With this arrangement the wires section 1' and 2 may, of course, be caused to move longitudinally either in opposite directions as in FIG. 4 or simultaneously up and down through the body B, as desired, Also combined such motions are imaginable.

FIG. 6 finally shows how the two wires section 1 and 2 may be imparteda longitudinal movement during the cutting operation by being each .continuouslyfed between a pair of storage dr-ums 11 and 12 respectively over-suitable pulleys 13. Also with the arrangementof FIG. 6 it.will obviously be possible to feed the two wiressection land 2 either in opposite longitudinal directions or in one and the same direction, the'direction of movement of each wire section being, however, unchanged throughout theqentire cutting process, which is contrary to the case of FIG. 5. Rewinding of the wires section may, of course, be effected between the cutting operations if it is notpreferred to have each wire section running in one direction during a first body cutting operation and then in the opposite direction during the nextbody cutting operation, in which latter case the rewinding problem is, of course, entirely avoided.

The running direction to be preferred for the" wires section of FIGS. 3 and 6 respectively in each particular case depends on several factors, above all on the support available for the light weight concrete body B during the cutting operation. Generally, the foremost wire section 1 should run in the very same direction as would have chosen in case this wire section had been the only one in the cut. In some cases, however, the wire section running direction is of no importance and, if several cuts are to be made in the body B, it may then be suitable to let the foremost cutting wires section in two adjacent cuts run in opposite longitudinal directions. Such an arrangement may also be applied when using reciprocating wires section as in FIGS. 4 and 5.

It should, of course, be understood that the specific mechanical arrangements, which have been hereinbefore described in connection with FIGS. 3 to 6 inclusive, have been selected for the purpose of illustration only and that there are several other arrangements available to obtain the same results as far as the longitudinal movements of the cutting wires section are concerned. Consequently the said examples must in no way be considered to limit the scope of the appended claims.

We claim:

1. A method of dividing an unhardened semi-plastic body of cellular lightweight concrete which comprises:

(a) penetrating a semi-plastic body with a first wire section that is caused to pass through. the body at an angle to the longitudinal axis of the wire section so as to thus produce a cut in the semi-plastic body,

(b) causing at least one following wire section to con tinuously follow closely behind said first wire section within the cut opened by said first wire section so that each following wire section will effect a smoothing of the walls of the cuts,

(c) each of the following wire sections that follow behind said first wire section having at least substantially the same thicknessas the said first wire section.

2. A method according to claim 1 wherein at least one of said following wir'esections has a direction of movement along its longitudinal axis during the course of its passa'ge'through the semi-plastic body. 1

3. The method of claim 1,.wherein thefirst-following wire section-and said first ,wire section are, both portions of a continuous wire length.

4. The method according to claim 1, wherein eachfollowing wire section is thicker than the next preceding wire section that has passed through the same cut, including the first cutting wire section.

5. The method according to claim 4, wherein each thicker following wire section is no more than twice as thick as the next preceding wire section in the same cut.

6. The method according to claim 2, wherein all wire sections passing through the same cut are moved in their longitudinal direction during their passage through the body to be cut.

7. The method according to claim 6, wherein said wire sections passing through the same cut are caused to move longitudinally in mutually opposite directions.

References Cited UNITED STATES PATENTS ROBERT F. WHITE, Primary Examiner.

S. I. LANDSMAN, Assistant Examiner. 

